Temperature Dependence and Anisotropy of Electron Drift Mobilities in Anthraquinone

Abstract

Electron drift mobilities have been measured in anthraquinone single crystals by the transient photoconductivity technique. At low temperatures the mobilities are trap controlled with trap depth of about 0.2 eV and concentration of about 100 p.p.m. At room temperature and above, the mobilities are practically trap free, 0.28, 0.20 and 0.022 cm²/V sec for the ć, b and a crystallographic directions, respectively.

Theoretical calculations do not predict the observed mobility anisotropy. Some possible reasons for this discrepancy, such as anisotropy of electron-phonon coupling, or underestimation of the role of the oxygen substituents in electron exchange are discussed.